The average wholesale price for a gram of medical cannabis leaf in Pennsylvania has fallen 36% since the beginning of 2020. But the average retail price that patients pay is down only 14% over the same period, a state official said Tuesday. That discrepancy “is a red flag that needs to be investigated,” the outgoing director of the state’s Office of Medical Marijuana, John Collins, said during an online meeting of the Pennsylvania Medical Marijuana Advisory Board. The average wholesale price of a gram of weed fell to $6.56 in February from $10.19 at the beginning of 2020. At retail, the averag…